Servovalves are very widely used in aircraft as well as in industrial processes and machine systems because they enable a great deal of power or large forces to be exerted in response to an electrical signal. In the present state of the art, however, extremely high precision is required, and this in turn demands that precise information be gained as to the performance of the servovalve under a great many different static and dynamic conditions. To this end, therefore, there have been developed servovalve analyzers which enable a number of parameters of a unit under test (UUT) to be measured. For a time, a product made by industrial measurements and controls, and described generally in U.S. Pat. No. 2,934,938 was widely used throughout the industry to derive essential servovalve analysis information. A knowledgeable operator could, using preset sequences and potentiometer settings, perform an allotted number of tests on a servovalve, the results of which were recorded on an XY plotter, the plots from which could be measured to derive certain essential values.
Subsequently, a data processor-based version of this system was introduced by industrial measurements and controls that was called the "Image 2000". This system was based upon the concept of making available a fixed number of predetermined programs and hardwired circuits for a specific set of servovalves and transducers. With all servovalve characteristics known in advance, this system could accommodate perhaps 20 different servovalves. Present needs, however, demand far more versatility and capability, as well as higher ranges of precision than have heretofore been available. There is a need for what is essentially a generic or universal servovalve analyzer, which can be utilized to analyze many different UUTs having widely varying pressure, flow rate and actuation requirements. It is desirable to accommodate these different servovalves without requiring the generation of new programs, without requiring dedicated systems requiring highly skilled operators for each different valve type, and without requiring readjustment of the system.
For example, servovalve characteristics are dependent on a number of principal factors, including pressure, flow rate, drive signal and the dimensional system (English or Metric) that is used. Analysis is then made of a number of principal parameters, such as flow gain, hysteresis, nonlinearity, asymmetry and saturation. Today, moreover, some or practically all of a number of other specific parameters have to be measured, including (but not limited to) null shift, null area flow gain, threshold, resolution, internal leakage, pressure gain, null pressure, dynamic response at preset points and proof pressure. Because servovalves range widely in size, power demands, pressure levels involved and other characteristics, various servo amplifiers having different current and power characteristics must be used to provide electrical stimuli, and different physical stimuli might also be utilized. Furthermore, because pressure, displacement (position) and flow rates must be measured, each possibly requiring sensing in a plurality of different ranges, many different transducers may have to be made available for each of these ranges. To be able to analyze a thousand or more different UUTs with the accuracy and versatility needed, but without requiring system reconfiguration by the operator or extensive additional programming or computational work, requires that problems be overcome that have not heretofore been faced.